Composition for treating airplane and similar fabrics



Patented Dec. 26, i922.

HEDLEY ROSS, OF BUFFALO, NEW YORK, ASSIGNOR- TOPRA'I'T & LAMBERT, OF

BUFFALO, NEW YORK, A CORPORATION OF NEW YORK.

COMPOSITION FOR TREATING AIRPLANE AND SIMILAR FABRICS.

N0 Drawing. Application filed July 19, 1918, Serial No. 245,605. Renewed November 11, 1922. Serial To all whomfit may concern:

ject of Great Britain, temporarily residing at 817 Richmond Avenue, city of Buffalo, State of New York, United States of America, have invented certain new and useful Improvements in Compositions for Treating Airplane and Similar Fabrics, of which the following is a specification.

As is well known, the wings, fuselage, rudders and other parts of air planes are constructed of frame work on which is stretched a fabric of linen, cotton or other suitable material, usually specially woven. To pre vent disintegration of the fabric by moisture, it is necessary to waterproof the same. It is also essential to the successful operation of the airplane that the fabric surface should at all times be kept taut, as any stretching or bagging of the fabric would cause inef ficient operation of the plane. It has been found impossible to apply the fabric to the framework with the desired degree of tuatness, or to maintain it in such. condition, without the use of some material that causes shrinkage of the fibres of the fabric and prevents changes in moisture and temperature conditions affecting the degree of tautness of the fabric. It has therefore become of great importance in the airplane art to provide a compound for impregnating and coating the fabric that will produce and maintain under all ,conditions, the desired degree of tautness of the fabric and at the same time satisfactorily waterproof the same. Ma-nifestly, it .is highly important that such composition should be non-inflammable and it is essential that it should have such degree of durability as not to disinte grate in use. Many compositions for treating the fabric of airplanes have been experimented with anda number have been usedto considerable extent in spite of obvious defects. Such compositions are known in the art by the technical name of dope.

The purpose of my invention is to provide an improved dope that iswaterproof and non-inflammable and that is so constituted as to give and maintain the requisite degree of tautness and to remain effective under all weather and service conditions.

It was well known prior to my invention that cellulose compounds, dissolved in suitable solvents, would afford the desired waterproofing qualities and the effect of fatty acid esters of cellulose, in particular acetyl cellulose, in rendering such a compound non-inflammable was also well known. It was also known that such a compound could be given a greater, degree of non-inflammability by the addition of well known fire retarding substances, such as organic silicates, as for example methyl silicate and ethyl silicate, organic substances such for example as tri chlor phenol and tri phenol borate, organic phosphoric esters such as tri phenyl phosphate, tri naphthyl phosphate, and variousinorganic substances, such as ammonium phosphate, magnesium phosphate, calcium chloride and numerous other substances. It was also known in' the art of manufacturing photographic films iggthat certain substances that evaporated only slowly and at high temperatures such for example as tri-phenyl phosphate (boiling point about 245 centigrade) caused the deposited cellulose to retain its flexibility and toughness thus rendering the same more durable and stable. The action of these va rious substances with respect to shrinkage of the fibres of the fabric and the production of a desired degree of tautness, and in respect to durability of the waterproofing and tension regulating compound under service conditions encountered in the use of airplanes were not understood. Experience showed that while acetyl cellulose wasnot inflammable relative to nitro cellulose the I former cracked, powdered, and disintegrated 'very rapidly under service conditions, and

it was also found that acetyl cellulose when used alone in a suitable solvent caused ex treme and undue tautness of the fabric; and that the colloidal deposit resulting from such solution, would disintegrate so rapidly as to render its use impracticable. The problem, therefore, was, to select such ingredients and to make such combination of such ingredients as would give a non-inflammable composition that had the necessary-qualities of shrinking the airplane fabric sufficiently and yet not unduly, thus giving the desired degree of tautness and at of the colloidal cellulose deposited in the the same time giving the composition such powers of resistance to weather effects and disintegrationunder conditions of airplane usage as to prevent the composition losing its tautening and waterproofing effect on the fabric. i

- As the result of a long series of experiments, I discovered that the shrinkage of the fabric caused by the use of such cellulose solutions was due to the contracting was more largely effected by the. action of the actinicrays of the sun. This led to a further search for a substance that would render the cellulose deposit durable under continued exposure'to the sun. The superior fire resisting qualities of acetyl cellulose as compared with nitro cellulose made it desirable to endeavor to modify and improve the former, though less durable than the latter. The testing ofa large number of possiblesubstances and combinations led to the discovery that the phosphoric ester known as triphenyl phosphate, when used in proper proportion relative to the acetyl cellulose content, has the double result of modifying and shrinkage action of the cellulose deposit and rendering even acetyl cellulose practically unaffected by the actinicrays of the sun and other weather conditions during the normal periods of use.

. While tri phenyl phosphate was found to have the most desirable action in the respects mentioned, tri cresyl phosphate, tri naphthyl phosphate and the other similar, substances have these qualities in varying degree. stances do not evaporate or disintegrate either. rapidly or at low temperatures, they also contribute in a desirable manner to the flexibility and durability of the coating renderingit less subject to disintegration by reason of vibrations and strains in the fabric.

The desirable results above referred to are directly dependent, however, upon the relative proportions of the acetyl cellulose or similar compound and thetension regulating and stabilizing agent, such as tri phenyl phosphate, as it is only between certain limits that the presence of the tri phenyl phosphate, or similtr agent and the acetyl cellulose compound will give the de- Owing to the fact that these sub-- sired degree of tautness and only within certain limits will prevent the disintegration of colloidal deposit. For example a compound containing one hundred parts by weight of acetyl cellulose and sixteen parts of tri phenyl phosphate would be ineffective to prevent a. very rapid disintegration of the cellulose deposit in the fabric of an air-.

plane exposed to sun light and varying weather conditions of moisture and temperature. Such disintegration would result in the uneven stretching of the fabric and penetration of the same by moisture, decreasing the efficiency of the plane and rendering its use dangerous. Furthermore the application of such a compound would cause the fabric of the airplane to be drawn so taut upon drying of the dope that the. framework would be liable to be distorted. Morephosphate or similar substance evaporating only at high temperatures adds to the durability of the coating and increases its stability under the usual conditions of airplane service.

On the other hand a dope composed of one hundred parts by weight of, acetyl cellulose and forty-eight to fifty parts of tri phenyl phosphate, dissolved in a suitable solvent, as for example acetone or methyl acetate, will draw the fabric only to the necessary degree of tautness without subjecting either the fabric or the framework to undue strain or creating undesirable tension in the colloidal deposit, which also possesses the desired toughness. According to practical tests of airplanes under regular service conditions, dope made in accordance with the formula last suggested has shown no signs of disintegration after many months of exposure to sunlight and varying-conditions of moisture, temperature and usage, and the fabric so treated and used in airplane service has retained its requisite tautness and has outlasted the other parts of the plane on which it was used.

I have found that in order to give the requisite tautness to the fabric and not unduly to stretch the same or strain the frame and not to create undue tension in the colloidol deposit, the dope solution should have a content of tri phenyl phosphate, or itsequivalent, not less than approximately thirty parts by weight and not more than approximately sixty parts by Weight to one hundred parts of acetyl cellulose, or its equivalent. If less than the above mentioned proportion of tri phenyl phosphate, or its equivalent, be used, the fabric to which it was applied'iwould be too tightly stretched and the colloidal deposit'under too high a tension, whereas if a larger proportion of such agent be used the fabric would not be sufficiently stretched.

In order that there may be imparted to the dope the desired resistance to the disintegrating effect of the sun and other than seventy parts of this agent were used weather conditions, there should be used to each one hundred parts by weight of acetyl cellulose or its equivalent, not less than about forty parts and not more than about seventy parts of tri phenyl phosphate, or its equivalent. If a substantially smaller proportion of such agent be used the durability of the resulting colloidal deposit would be seriously impaired, and if more phenyl phosphate in proportions within the limits above mentioned common to both examples above given, namely, one hundred parts by weight of acetyl cellulose to from forty to sixty parts of tri phenyl phosphate,

which ingredients are dissolved in a desired manner, either separately or together, in a sufiicient quantity of acetone or methyl acetate or similar solvent or mixtures thereof, to produce a solution having such a degree of viscosity as readily to penetrate the fibre of the fabric as well as to cover the surface thereof. The quantity of solvent to be used depends upon the character'of the acetyl cel lulose, which, as is well known, differs in solubility and can easily be determined by v one familiar with the art. If desired, a proportion of high boiling point solvent, such as benzyl alcohol, benzyl acetate and diacetone alcohol may advantageously be used under certain conditions. These solvents are of suflicie ntly' high boiling point to evaporate slowly and to thus prevent the sudden chilling and consequent absorption of moisture from the air that would occurjf rapidly evaporating solvents of lowboiling points were used. In the latter case the cellulose ester would be deposited in its original amorphous state producing the undesirable condition known in, the art as blushing; the use of the high boiling point solvents above referred to results in the gradual deposition of the cellulose esterfrom the solution in the desirable colloidal state. I have discovered that propylene chlorhydrin is especially good for this purpose, as its boiling point is in the neighborhood of 160 degrees Centigrade and its presence in small proportion will prevent thewhitening of the depositfrom the dope in humid weather.

The following are typical examples of formulae embodying my invention, giving shrinka e and durability effects combined.

(1) fine gallon acetone, eight ounces acetyl cellulose, three ounces tri phenyl phosphate.

(2) One gallon methyl acetate, one gallon acetone, one pound acetyl cellulose, eight and one-half ounces tri phenyl phosphate.

In connection with the dope, protective material such as paint or varnish may also be used to further protect the cellulose deposit against water, light and wear. A min eral paint which has considerable body may be used'for this purpose but in particular a paint that is opaque to actinic rays is especially desirable as even when tri-phenyl phosphate is used and in the proportions above stated the presence of the material opaque to actinic rays lessens the'liability of the cellulose deposit to disintegration, This protective material may be applied either as a final coating or may be mixed with the last coating of the dope. In either case it adds to the wearing qualities of the; dope and lessens the tendency of the solvents in the dope to evaporate.

It should be understood, however, that instead of using a formula combining to the full degree the characteristics above setforth of properly tensioning the fabric, and also of giving the desired durability to the colloidal deposit the same result can be accomplished by applying one or more ground coats of dope giving the desired tensioning eifect to the fabric and subsequently applying one or more finish coats giving the desired durability to the colloidal deposit. In usual practice two or more ground coats would first be applied and then two or more finish coats. Such ground coats designed to give the required tautening effect might, as above pointed out, be made of one hundred parts of acetyl cellulose and from thirty to sixty parts of tryphenylphosphate or its homologues, dissolved in suitable solvent or anyother suitable regulating agent might be added to. the celluloseester so that the colloidal deposit resulting from the evaporation of a solution of the same when applied to the fabric would have the desired degree of tautening effect. The finish coat designed to give to the colloidal deposit the desired degree of durability against the dis integrating action of the sunlight and weather may, as above pointed out, be made of one hundred parts of acetyl cellulose or its quivalents with from about forty to seventy parts of tryphenylphosphate or its homologues dissolved in suitable solvent.

v While the compound herein described is intended especially for use for airplanes, it

is, of course, suitable for treatment of other fabrics used under similar conditions or involving similar requirements.

I do not intend to limit myself to the exact disclosures herein made as it is evident that modifications may be used without departing from the spirit of my invention.

Vfhat I claim as my invention is set forth as follows:

1. A composition for treating aeroplane.

and similar fabrics comprising acetyl cellulose in approximately 100 parts by weight, tripheriyl phosphate in approximately from to 60 parts by weight dissolved in a solvent.

2. A composition for treating aeroplane and simllar fabrics comprislng a relatlvely non-inflammable cellulose ester, a phosphoric ester in weight approximately of the cellulose ingredient anda volatile solvent for the ester. v

3. A composition for treating aeroplane and similarfabric's comprising acetyl cellulose, t riphenyl phosphate in quantity approximately 50% by weight of the cellulose ingredient, a volatile solvent for said ingredient and a high boi'ling point solvent.

4-. A composition for treating aeroplane and similar fabrics comprising acetyl cellulose, triphenyl phosphate in quantity from between approximately 40% to by weight of the cellulose ingredient, a-vola tile solvent for said ingredients, and propylene chlorhy-drin.

5. A composition for'treating aeroplane non-inflammable cellulose ester, a volatile' solvent and added material having a boiling point approximately 245 C, whereby added durability is imparted to the cellulose deposit. I

7. A composition for treating aeroplane and similar fabrics comprising arelatively.

noninflammable cellulose ester, a volatile solvent and added material having aboiling point approximately 2459 G, whereby added durability is imparted to the cellulose deposit and also a slowly evaporating solvent having a boiling point inthe neighborhood of, ;C., whereby the slowly evaporating solvent permits gradual deposition of the cellulose ester without whitening effect.

HEDLEY' ROSS. 

